Two days after two bombs tore through a crowd of spectators at the Boston Marathon, little is known about the motive or culprit(s). The explosive devices, which killed three people and injured more than 180, could have cost as little as $100 to build and were made of ordinary ingredients.

Dzhokhar Tsarnaev, a suspect in the bombings, is charged with using a weapon of mass destruction and, if convicted, could face the death penalty. The April 15 bombings killed three people and injured more than 260.

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Dzhokhar Tsarnaev, a suspect in the bombings, is charged with using a weapon of mass destruction and, if convicted, could face the death penalty. The April 15 bombings killed three people and injured more than 260.

Massachusetts Governor Deval Patrick appeared on CNN this evening and spoke about the ongoing investigation. The Post’s Jerry Markon was able to capture these remarks:

Patrick, who has been briefed, said the investigation is “making some progress” but “it’s going to be slow, it’s going to be methodical…this is going to take some time, a lot of time.’’

“It does seem like they are doing this in a very methodical way,’’ said Patrick, who asked the public for “patience.’’ He also said he didn’t think there would be an FBI briefing tonight, but could not say for sure.

“The service is an opportunity for the community to come together in the wake of the tragic events at the Boston Marathon this week,” Patrick and Menino said in the announcement.

Doors will open to the public at 8 a.m. and tickets will be available on a first come, first serve basis. Patrick and Menino’s message warned the public to expect “airport-like security,” and also advised people to be prepared for lines and delays.

The mild chaos of Wednesday afternoon, which saw some media outlets erroneously report that a suspect was in custody, briefly drowned out what seemed to be the biggest development in the bombing investigation so far.

That development centers on video recordings that officials say is being used as part of the investigation. Investigators are combing through video footage from a Lord & Taylor camera, with a Boston city official telling The Washington Post that the camera is of “special interest.”

Reuters reported shortly before 5 p.m. that investigators have spotted a possible suspect in the footage. But the Reuters report also stressed that a possible suspect spotted in footage is not the same thing as a suspect identified or in custody:

No arrests had been made, and the suspect in the video had not been identified by name, two government officials said. Police may make an appeal to the public for more information at a news conference scheduled for later on Wednesday, a government source said.

That news conference, originally scheduled for Wednesday at 5 p.m., was postponed following the evacuation of a federal courthouse in Boston. It’s unclear when this news briefing will occur, but stay with us for the latest developments.

There was major confusion on Wednesday afternoon as several media outlets offered very different claims about the arrest of a potential suspect in the bombings. It turned out that no arrest was made and no suspect was in custody, something the FBI and Boston Police Department both pointed out.

After the bombings in Boston, law enforcement officials asked for any photos, videos and tips the public could provide. Since we live in a time where so many people record life online in Instagrams, tweets and other posts, it seemed like some clues could exist in the information already available on the Internet.

For some Internet vigilantes, that meant it was time to search for clues online to help the official investigation. Others felt any online crowdsourced sleuthing could wrongly accuse innocent people. My colleague Caitlin Dewey has the story:

Apparently convinced they could supplement the FBI’s Boston marathon investigation, Internet vigilantes on Reddit, 4chan and other online message boards began their own crowdsourced sleuthing shortly after midnight on April 17. But as annotated photos from the scene went viral, some of the self-styled sleuths seemed to back off their quest — noting, as many critics had already, that vigilante meddling could hurt innocent people.

“You may get lucky and your pet suspect turns out to be the bomber,” reads a warning post on the Reddit thread “findBostonbombers.” “But I’ve seen at least 10 people singled out, and not all of you are correct. You should be very very careful about picking and choosing who you think might have killed three people and wounded many more, based on where they were standing and if they were carrying a backpack or not.”

The Washington Post’s David A. Fahrenthold files this report from Boston:

Boston’s federal courthouse, where hundreds of reporters and onlookers had gathered outside in response to false reports of an arrest in the marathon bombings, is being evacuated. Security officers gave no details, telling reporters to “break up” and move back away from the waterfront courthouse. Two K-9 teams from Federal Protective Services had approached with lights and sirens going.

From inside the courthouse, both employees in suits and children from the daycare poured out. Daycare workers pushed cribs with wheels on them, carrying the smallest children inside and away from the building.One officer on the scene said the scene was caused by a bomb scare, but there was no other corroboration of that.

The Boston Globe was also reporting that in addition to the courthouse, Brigham and Women’s Hospital was also being evacuated:

BREAKING NEWS: Federal court is being evacuated and a witness says Brigham and Women’s Hospital is also being evacuated.

The FBI released this statement in response to the flurry of contradictory reports regarding an arrest:

Contrary to widespread reporting, there have been no arrests made in connection with the Boston Marathon attack. Over the past day and a half, there have been a number of press reports based on information from unofficial sources that has been inaccurate. Since these stories often have unintended consequences, we ask the media, particularly at this early stage of the investigation, to exercise caution and attempt to verify information through appropriate official channels before reporting.

But this also adds to an extremely chaotic, uncertain scene unfolding on news channels and social media outlets. Multiple outlets reported that a suspect was in custody (including the Associated Press, CNN and the Boston Globe), but many others contradicted that by saying that no arrest was made and no one was in custody (including NBC News and CBS News).

The uncertainty was particularly noticeable on cable news, as CNN initially reported that an arrest was made and eventually backtracked, and on Twitter, where conflicting reports began streaming out shortly before 2 p.m.

Yesterday, investigators revealed that the explosions at the Boston Marathon were the result of simply designed pressure cooker bombs. Today our Graphics Department put together a visual explainer of how they work. Click the image below for the full graphic.

Graduate student Lingzi Lu was identified Wednesday as the third person killed in the Boston Marathon bombings.

Boston University said Lu, a student there, was watching the race with two friends when the bombs detonated near the finish line. She was a graduate student in mathematics and statistics.

Her precise identity remained unclear for two days, as authorities in China and the U.S. did not released her name. My colleague Steven Mufson reports that Ma Shizun, a reporter for the Shenyang Evening News, wrote an article in Wednesday’s newspaper saying the Lu was missing. Mufson also says the article was accompanied by her photograph. Tomorrow’s newspaper carries a story saying that a local Shenyang student was killed in the explosion in Boston without mentioning her name, Mufson added. The reporter spoke to the family, which asked that her privacy be respected.

The Associated Press is reporting that an arrest is “imminent,” according to a federal official.

However, there are multiple news outlets reporting conflicting information about a potential suspect in the bombings case and whether or not an arrest has taken place.

CNN is reporting that an arrest has been made. John King first reported this news just after 1:45 p.m. The Boston Globe also reported that an arrest was made. NBC’s Pete Williams, meanwhile, reports that no arrest has been made.

We don’t know for sure which, if any, of these reports are accurate. But we will update with the latest developments as they occur.

An official briefed on the Boston Marathon bombing investigation said today that authorities have an image of a suspect carrying, and perhaps dropping, a black bag at the second bombing scene on Boylston Street, outside of the Forum restaurant.

A spokeswoman for Boston Mayor Thomas Menino told the Globe that the video at Lord and Taylor is the best source of video thus far.

CNN’s John King has reported that a law enforcement source told him that officials have “made a clear identification of a potential suspect.”

King said the information was gleaned from video footage taken from a Lord and Taylor store near the second explosion. He also said sources told him that this video footage and other footage helped possibly identify a suspect.

The Boston Globe also is reporting that a source says officials are “very close” in the investigation of the bombings. The Globe reported that authorities have an image of a potential suspect “carrying, and perhaps dropping, a black bag” at the scene of the second bombing.

Guards were in place Monday night at Brigham and Women’s Hospital. (Stan Honda/AFP Getty Images)

There’s a reason why the response to the Boston Marathon bombings was so methodical, and was carried out with such crisp professionalism.

Apart from the fact that race organizers have medical tents set up along the route and at the finish line for runners, the city’s hospitals were ready, its medical personnel prepped and dedicated. Atul Gawande, a physician at Brigham and Women’s Hospital, writes at NewYorker.com:

What prepared us? Ten years of war have brought details of attacks like these to our towns through news, images, and the soldiers who saw and encountered them. Almost every hospital has a surgeon or nurse or medic with battlefield experience, sometimes several. Many also had trauma personnel who deployed to Haiti after the earthquake, Banda Aceh after the tsunami, and elsewhere. Disaster response has become an area of wide interest and study. Cities and towns have conducted disaster drills, including one in Boston I was involved in that played out the scenario of a dirty-bomb explosion at Logan Airport on an airliner from France. The Massachusetts General Hospital brought in Israeli physicians to help revamp their disaster-response planning. Richard Wolfe at the Beth Israel Deaconess recalled an emergency physician’s presentation of the medical response required after the Aurora, Colorado, movie-theatre shooting of seventy people last summer. From 9/11 to Newtown, we’ve all watched with not only horror but also grave attention the myriad ways in which the sociopathy of killers has combined with the technology of inflicting mass casualty.

We’ve learned, and we’ve absorbed. This is not cause for either celebration or satisfaction. That we have come to this state of existence is a great sadness. But it is our great fortune.

Pierre Rouzier, a doctor for sports teams at the University of Massachusetts, was a marathon volunteer who was 50-100 yards from the first explosion and ran to help.

“In a strip of sidewalk that was maybe 20 feet by 40 feet, there were probably Kevin Wares,” Rouzier told the Denver Post’s Benjamin Hochman, referring to the Louisville basketball player who suffered a compound tibia fracture in the NCAA tournament. “People with open tibia fractures. One poor kid had both legs blown off.”

Rouzier told Hochman that he worked until all that remained was “blood and glass.” There was no time for chatter.

“I wish,” Rouzier said, “that I had gotten some names of the people. You needed it to be mechanical — do the right things for their limbs, legs and injuries — and I wished I had made it personal and gotten their names. I was treating limbs; I wish I was treating hearts and souls.”

CNN is reporting that progress has been made in the Boston investigation.Wolf Blitzer was on the air shortly after 12:30 p.m. announcing that CNN’s John King had learned that “substantial progress” has been made, but he didn’t provide any additional details.

While these events are adding to what is already a considerably tense time in the U.S., a law enforcement source tells Reuters that there’s no indication these letters are connected to the Boston bombings. [UPDATE: The FBI said in a statement that there’s “no indication of a connection” between the letters and the bombings.]

Joe Andruzzi, the former NFL player shown carrying a woman from the scene of the Boston Marathon bombings, insists he did nothing heroic.

“I am definitely not a hero,” Andruzzi, 37, told the Boston Globe on Tuesday. “I am just a bystander, and that led to my help. Many heroes that I look upon are people like my three brothers that are running into burning buildings when others are running out. Explosions are going off and they are driving their cars down Boylston [Street] right into the heart of the scene. They are the people that don’t care about their safety and are worried for other people’s safety and survival.”

Andruzzi’s brothers are New York City firefighters who were among the first responders on Sept. 11, 2001. Andruzzi said he didn’t get the name of the woman he helped in the photo, but that he knows she is from Virginia and was watching with her three daughters at the finish line.

“It was starting out to be a great day, great event and unfortunately it did not end up that way,” Andruzzi said.

Updated: 11:15 a.m. The bomb squad has opened the truck and it was empty, News 9 reports. But the outlet also notes that police haven’t given the all-clear, as they are still examining the truck.

Earlier: A suspicious U-Haul truck parked near City Hall in Oklahoma City has prompted the evacuation of several buildings and the closure of several streets, according to local news outlet News 9.

It should be noted that at this point, this is just a report of police investigating a suspicious vehicle. There is a considerable atmosphere of fear in the wake of the Boston bombing. We saw this on Tuesday as a LaGuardia Airport terminal was evacuated and a US Airways plane held on the tarmac at Logan Airport, both for what turned out to be false alarms.

But this report is noteworthy given that Friday is April 19, the anniversary of the 1995 Oklahoma City bombing attacks that killed 168 people.

Police, according to NewsOK.com, are using a robot at the moment to examine what it says is a stolen vehicle.

The New York Times has posted a helpful visualization of where the two explosions occurred at the Boston Marathon. If you’re trying to wrap your brain around exactly where the two bombs exploded — both in terms of the race and where they occurred on the street — this could help.

Media outlets regularly grapple with how to handle graphic violence and bloodshed: How much can we or should we show?

The issue cropped up again after the Boston bombings, as a large number of gruesome photos and videos from the scene quickly spread across the Internet.

Joe Pompeo of Capital New York is pointing out that the New York Daily News may have altered the photo that ran on its cover on Tuesday.

[T]he version published by the News seemed to erase a gory wound to the woman’s leg that was visible in other publications that used the photo. On Tuesday evening, a link to a blog post exposing the manipulation began circulating among News journalists, some of whom were none-too-pleased about the situation, multiple newsroom sources told Capital.

This seems to be the second time this month that the Daily News has altered a photo. The outlet tweaked a picture of Jay Leno and Jimmy Fallon to accompany a story about “The Tonight Show” changing hosts.

To see the graphic original photo — and remember, the photo is graphic, so keep that in mind — head to Capital New York.

On “The Colbert Report” on Comedy Central, Stephen Colbert praised Bostonians, “a people so tough they had to buckle their hats on.”

“Whoever did this obviously did not know about the people of Boston. Because nothing these terrorists do is gonna shake them. … A city that withstood an 86-year-losing streak. A city that made it through the Big Dig – a construction project that backed up traffic for 16 years. I mean, there are commuters just getting home now.”

In the first episode of “The Daily Show” since the Boston bombings, Jon Stewart offered a simple message: “Thank you for once again in the face of gross inhumanity, inspiring and solidifying my belief in humanity and the people of this country.”

Bostonians and New Yorkers have managed to put aside their long, colorful rivalry — the one related to “suckitude” — at least for a little while.

“We are your brothers and sisters in this type of event. As a city that knows the feeling of confusion, anger and grief and chaos that comes from these events, I can tell you from personal experience, you got a hell of city going on and you’ve done an incredible job in the face of all this.”

Investigators have found the lid of a pressure cooker that was seemingly “catapulted onto the roof of a nearby building,” the Associated Press is reporting. A law enforcement official confirmed to the AP that pieces of the explosive devices have been recovered.

My colleagues Joby Warrick and Sari Horwitz reported that the bomb was made with very ordinary ingredients:

Investigators revealed Tuesday that fragments recovered at the blast scene suggest a simple design: a common pressure cooker of the kind found at most discount stores, packed with an explosive and armed with a simple detonator. A final ingredient — a few handfuls of BBs, nails and pellets — helped ensure widespread casualties when the two devices exploded Monday near the race’s finish line, law enforcement officials said.

The FBI agent heading up the inquiry, Richard DesLauriers, said that pieces of the bombs and residue were sent to the FBI laboratory in Quantico, Va., for testing.

Another widely-reported aspect of the bombs has been the black nylon found at the scene, which investigators said suggests that at least one bomb was concealed in a bag or backpack.

Secretary of State John F. Kerry, making his first appearance before Congress in his new job, appeared to choke up as he praised the citizens of Boston. The granddaughter of one of his strongest political supporters there, whom he did not name, is “fighting to keep her legs,” he said. His voice breaking, the former Massachusetts senator said “we’re not going to be intimidated by this. We’re going to find out who did this.”

The race, organizers of the Boston Marathon vow, will go on in 2014. In fact, note it now: Patriots Day, April 21, 2014.

“We are committed to continuing that tradition with the running of the 118th Boston Marathon in 2014,” said Tom Grilk, head of the Boston Athletic Association.

But just what kind of race will it be? And how will this affect other marquee marathons? Charles P. Pierce has covered a couple dozen of the marathons and writes on Grantland.com that “the marathon was the old, drunk uncle of Boston sports, the last of the true festival events.” It will now, of necessity, change.

Every other one of our major sporting rodeos is locked down, and tightened up, and Fail-Safed until the Super Bowl now is little more than NORAD with bad rock music and offensive tackles. You can’t do that to the Marathon. There was no way to do it. There was no way to lock down, or tighten up, or Fail-Safe into Security Theater a race that covers 26.2 miles, a race that travels from town to town, a race that travels past people’s houses. There was no way to garrison the Boston Marathon. Now there will be. Someone will find a way to do it. And I do not know what the race will be now. I literally haven’t the vaguest clue.

If the London Marathon, which takes place Sunday, is any guide, Pierce is right. London’s race will attract about 36,000 runners with 500,000 along the 26.2-mile course and Prince Harry handing out medals to the winners. Sir Bernard Hogan-Howe, the Metropolitan Police commissioner, said authorities were “taking more more precautions than we might have done otherwise.”

“We will make sure we’ve got more officers on the street looking after people, making sure they’re kept safe, but we’ve no reason to think they’d be any less safe than before the terrible events in Boston,.” he said (via NBC News). “We’d be professionally irresponsible if we didn’t take some reasonable steps.”

A 5-year-old boy is one of two Boston Marathon bombing victims who remain in critical condition at Boston Medical Center, Dr. Peter Burke, the hospital’s head trauma surgeon, said in a briefing this morning.

Another victim, a 65-year-old man, is listed as critical, with 10 patients in serious condition and seven fair. Among the other bits of information Burke supplied: there have been seven amputations performed on five patients and 19 out of 23 victims the hospital received remain hospitalized, with eight some facing facing more surgery today. Burke explained that, in trauma, doctors wait to close wounds until they see that there’s no infection, that the tissue is “viable.” Treating trauma is a process, not a momentary thing.

“I will not be happy until they are home.” Burke said. “I will not be satisfied.”

One or two patients could be released today, Burke said, and 10 were originally listed as critical when they arrived.

The two bombs that exploded at the Boston Marathon are believed to have been in pressure cookers and, this morning, the lid to one of those pressure cookers was found on the roof of a building at the finish line.

CNN reported the discovery, which could be a fairly significant break. The pressure cookers, filled with nails and ball bearings, were in black backpacks and part of the debris from one of those backpacks has been found as well.

The remains of one backpack, from an FBI/Department of Homeland Security joint bulletin. (AP Photo/FBI)

The devices’ design, The Post’s Joby Warrick and Sari Horwitz reported, was immediately recognized by counterterrorism experts as a type touted by al-Qaeda and one similar to those used by terrorists in mass-casualty bombings in numerous countries, from the Middle East to South Asia to North Africa.

Part of a pressure cooker found at the scene. (AP Photo/FBI)

The common components of the bomb will, however, make investigators’ work that much more difficult.“This is going to take a very long time,” a federal law enforcement official told The Post.

The second full day since the marathon attacks has dawned with yet more painstaking work to be done by investigators, even as the injured begin to recover and mourning continues for the three people who were killed Monday.

Of the more than 180 people who were injured, 100 have been released from Boston-area hospitals, CNN reports this morning.

On Tuesday night, a memorial for 8-year-old Martin Richard was held near the baseball diamond where he played in his Dorchester neighborhood. The Rev. John Connolly of St. Brendan Catholic Church told mourners in the brief service (via Huffington Post):

“What once seemed to be something we watched in the distance or on television has come all too close to home. Upon this field, the feet of young Martin often trode. We are saddened and shattered by the fact that he will not longer run and smile and jump and play and live and love among us. Nothing we can say, and nothing we can do, is adequate in the face of the enormity of that sadness.”